As an example of a display apparatus of this type, in Japanese Patent No. 5,610,499 the present applicant disclosed a display apparatus for advertising on utility poles. This display apparatus is configured so that when mounted on the outer circumferential surface of a utility pole, a light guide plate emits light across a plane so as to illuminate (or “backlight”) an advertising medium (display medium), which is disposed on the front side of the light guide plate, from the rear. More specifically, the signboard apparatus disclosed by the present applicant includes a frame (substrate), LED light sources (or “strip-like light sources”), a light guide plate, a transparent display board (or “surface plate” or “cover plate”), a first spacer, a second spacer, and the like.
The frame includes a mounting frame that is curved in keeping with the outer circumferential form of a utility pole and a display frame that has a display window portion formed in a center thereof and is fixed to the mounting frame so as to be disposed on the front side of the mounting frame. A white coating is applied to the front surface of the mounting frame so that the surface functions as a reflective surface. Bent-over portions that are bent over toward the front are formed at both end portions in the width direction of the mounting frame to provide spaces that house the LED light sources, the two spacers, and the like.
The LED light sources are housed in the housing spaces described above in the mounting frame so as to be sandwiched between the two spacers, i.e., the first spacer and the second spacer, and emit light toward the end surfaces (or “incident end surfaces” or “side end surfaces”) of the light guide plate. The light guide plate is curved so as to match the reflective surface of the mounting frame and is disposed on the surface side of the mounting frame. This display apparatus is configured so that the posture in which the LED light sources are mounted on the mounting frame is regulated by the two spacers so that light from the LED light sources becomes incident at an angle on the end surfaces of the light guide plate.
The transparent display board is a plate-like member that acts together with the light guide plate to hold the advertising medium and is curved in the same way as the light guide plate. The first spacer and the second spacer are configured of metal rods of an arbitrary diameter that are capable of regulating the mounting posture of the LED light sources on the mounting frame, that is, of regulating the incident angle of light on the end surfaces of the light guide plate attached to the mounting frame. Note that although the display apparatus includes a backing material, a sealing material, and the like aside from the component elements described above, such description of these elements is omitted here.
When assembling this display apparatus, a frame is first fabricated by fixing the display frame to the mounting frame. Next, the light guide plate, both spacers, the transparent display board, and the like are inserted from end portions (openings) in the length direction of the frame. After this, the LED light sources are inserted from the end portions in the length direction of the frame so as to be sandwiched by the two spacers. By doing so, the display apparatus is completed.
With this display apparatus, light that is incident at an angle on the end surfaces of the light guide plate is evenly guided across the entire area of the light guide plate and emitted from the light guide plate. Here, the light emitted toward the rear of the light guide plate is reflected by the reflective surface on the mounting frame so as to pass back through the light guide plate and be emitted to the front of the light guide plate. By doing so, the entire area of the light guide plate emits light and the entire area of the advertising medium disposed between the light guide plate and the transparent display board is brightly illuminated.